MCL injury is also part of the  Unhappy Triad , or the common injury of the MCL, ACL, and Meniscus all together, usually through a pivot shift type of mechanism.The most obvious sypmtom of MCL injury is pain. Following the injury, you will experience pain in the knee, usually along the iside of the joint.CL injury is also part of the  Unhappy Triad , or the common injury of the MCL, ACL, and Meniscus all together, usually through a pivot shift type of mechanism.
With hemangiosarcoma, the pericardium fills up with blood due to rupture of the tumor. When the tumor occurs in the skin, a mass or lump can usually be felt in or under the skin. The mass may become ulcerated and bleed. When the tumor occurs in a bone, it can cause pain and discomfort.
You can throw clots from the left side of your heart too (they cause strokes, etc...) typically from heart arrythmias, but they, by definition, travel in arteries... A hematoma on the other hand is the leaking of blood from a vessel..and if you can see it, it is probably a superificial, or shallow vessel. These are not responsible for throwing clots. As well, your hematoma is outside the vessel wall, which is why bruises gets to be big, and thus the coagulated blood is not a risk to get back into your veins and travel... Needless to say, don't worry.